Water from rain and melting snow that flows over lawns, parking lots and streets is known as stormwater runoff. This stormwater runoff may flow through gutters, into catch basins, through storm drain pipes and ditches, or over streets and paved areas. Along the way, the stormwater runoff picks up trash (fast-food wrappers, cigarette butts, Styrofoam cups, etc.) and toxins, bacteria and other pollutants (such as gas, motor oil, antifreeze, fertilizers, pesticides, and pet droppings). This stormwater runoff is usually not treated, and is discharged into local surface waterbodies and groundwater.
This polluted stormwater runoff can contaminate drinking waterbodies, it can force the closing of beaches because of health threats from harmful bacteria to swimmers, including those from Harmful Algal Blooms (HABs), it can kill fish and other wildlife, and it can destroy wildlife habitat.
In most towns, the Department regulates stormwater runoff from municipal separate storm sewer systems (MS4s) owned or operated by towns and other MS4 permittees in the state via the MS4 General Permits. The Department has also issued the Combined Sewer Overflow (CSO) permits to regulate stormwater in 21 towns that have combined stormwater and sanitary sewage systems.
Human activity is the primary cause of stormwater pollution. Everything that we put on the ground or into the storm drain can end up in our water. Each of us has a responsibility to make sure these contaminants stay out of our water.